An in-situ fabrication method for a silicon solar cell includes the following steps: pretreating a silicon chip; placing the pretreated silicon chip in an implantation chamber of a plasma immersion ion implantation machine; completing the preparation of black silicon via a plasma immersion ion implantation process; making a PN junction and forming a passivation layer on the black silicon; after making the PN junction and forming the passivation layer, removing the black silicon from the plasma immersion ion implantation machine; preparing a metal back electrode on the back of the black silicon; preparing a metal grid on the passivation layer; obtaining a solar cell after encapsulation. Said method enables black silicon preparation, PN junction preparation, and passivation layer formation in-situ, greatly reducing the amount of equipment needed for the preparation of solar cells and the preparation cost. In addition, the method is simple and easy to control.